Multi-phase brushless DC motors require specific drive signals to be supplied to each of the motor windings in order to obtain proper rotation of the motor. The relative position and timing of each of these drive signals, to each of the windings, is referred to as commutation and is the subject of a significant amount of work in the motor arts.
In that area, integrated circuit devices have been developed which provide circuitry for generating the drive signals and controlling the relative timing of the application of the drive signals to the motor windings. Among these integrated circuit devices are device number UC3620 manufactured by Unitrode Corporation, Lexington, Mass., and device numbers UDN-2936W and UDN2937W, manufactured by Sprague of Worcester, Mass. These integrated operate off of the power supplied to the motor and are therefore dependent upon a correct polarity of the motor power supply to operate properly. More specifically, these devices expect a positive voltage to be applied to a specific pin and a ground potential to be connected to another specific pin. Reversal of the polarity of potential supply to the pins will cause the devices to be inoperative and perhaps their destruction.
Reversal in direction of rotation of motors controlled by the above integrated circuit devices is obtained by applying a direction control signal to a direction control pin.
Thus, a disadvantage of controlling multi-phase DC brushless motors with these integrated circuit devices or devices similar thereto, is the need to pay particular attention to the polarity of voltage being applied to the devices and to the motor, and the further requirement of applying a direction control signal to a direction control pin to obtain the proper direction of rotation.